This invention relates to devices for distinguishing between opposed directions of motion of a part.
Heretofore, devices for distinguishing between opposite directions of motion of a part have included sensors displaced from each other in the direction of motion of the part, and they require a relatively large expenditure, particularly since their positioning depends upon the distance between optical or magnetic variations in the part.
German Offenlegungsschrift No. 3 134 020 discloses an apparatus for determining the speed and direction of rotation of a shaft which has a rotor of soft magnetic material with a plurality of radially directed poles disposed at different angular spacings and a stator with two oppositely energized excitation coils and a detecting coil. The apparatus is arranged so that the two excitation coils induce oppositely directed voltage signals in the detecting coil, and the direction and speed of rotation of the shaft are determined from the time sequence and direction of the detected voltage signals. This apparatus is costly, not only in terms of structural expense and space required, i.e., several coils on one stator, some with outside excitation, but also in terms of manufacturing cost because of the complicated rotor structure.
An optoelectronic motion-detecting device disclosed in German Offenlegungsschrift No. 3 709 182 is intended only to distinguish between two directions of motion of an element which are at an angle of less than 180.degree.. That device has a slit and a diaphragm partially occluding the slit disposed between a source of light and two photodetectors, the slit and the diaphragm being arranged so that, upon motion of the element in one direction with slit edges oblique relative to that direction of motion, the size of slit intervals extending along both edges changes in the same sense, whereas upon motion of the element in a direction perpendicular thereto the size of the slit intervals changes in opposed senses. The signals produced by these changes are processed to obtain direction-of-motion signals.
Finally, German Offenlegungsschrift No. 3 113 538 discloses a device for identifying the direction of motion of a vehicle by providing magnetic induction loops. In that device, the absolute values of the rising and falling slopes of a nonsymmetric signal generated by an induction loop of magnetically asymmetrical, for example triangular, configuration are taken as a criterion for identifying the direction of motion. That disclosure deals with a special case, i.e., an arrangement for road traffic control and, moreover, it utilizes a very specific technology, i.e., induction loops which generate nonsymmetric signals, thereby requiring an active electromagnetic system.